In recent years endovascular implantable devices have been developed for treatment of aortic aneurysms. These devices are delivered to the treatment site through the vascular system of the patient rather than by open surgery. The devices include a tubular or cylindrical framework or scaffolding of one or more stents to which is secured a tubular shape of graft material such as woven Dacron, polyester polytetrafluoroethylene or the like. The devices are initially reduced to a small diameter, placed into the leading or proximal end of a catheter delivery system. The delivery system is inserted into the vascular system of the patient such as through a femoral incision. The leading end of the delivery system is manoeuvred to the treatment site over a previously positioned guide wire. Through manipulation of a control system that extends to the proximal end of the catheter from the distal end of the system outside the patient the implantable device is then deployed by holding the device as its location and withdrawing a surrounding sheath. The stent graft or implantable device can then be released and self expand or be expanded through the use of a balloon which is introduced with the stent graft introducible device. The stent graft becomes anchored into position to healthy wall tissue in the aorta such after which the delivery system is removed leaving the device in position thereby bypassing an aneurysm in the aorta in a manner that channels all blood flow through the stent graft so that no blood flow enters the aneurysm, such that not only does the aneurysm no longer continue to grow and possibly rupture but the aneurysm actually begins to shrink and commonly disappears entirely.
For treatment of thoracic aortic aneurysms in particular it is necessary to introduce the implantable device high up in the aorta and in a region of the aorta which is curved and where there can be strong blood flow.
In the thoracic aorta there are major branch vessels, the brachiocephalic, the left carotid and the left subclavian and for treatment of an aneurysm in the region of the thoracic arch provision must be made for blood supply to continue to these arteries while an operation is in progress and after completion of the operation. For this purpose fenestrations or side branches are provided into a stent graft in that region. Access is generally obtained to these fenestrations to deploy side arms into the stent graft via the left or right brachial arteries or less commonly via the left or right carotid arteries. Once a guide wire has been introduced towards the thoracic arch via such an artery the fenestration must be accessed and then catheterised. For this reason it is desirable to provide an arrangement where access and subsequent catheterisation is possible even if there is a degree of mis-alignment between the fenestration and the respective branch artery.
The disclosure will be discussed in relation to a stent graft suitable for the thoracic arch of a patient but it is not so limited and may be applicable to any body cavities where access into a prosthetic device such as a stent graft is required from a side branch vessel.
Throughout this specification the term distal with respect to a portion of the aorta, a deployment device or a prosthesis means the end of the aorta, deployment device or prosthesis further away in the direction of blood flow away from the heart and the term proximal means the portion of the aorta, deployment device or end of the prosthesis nearer to the heart. When applied to other vessels similar terms such as caudal and cranial should be understood.